This invention relates to load pull testing of microwave power transistors employing automatic microwave impedance tuners, which allow synthesizing reflection factors (or impedances) at the input and output of said transistors at various harmonic or non-harmonic frequencies [1].
Modern design of high power microwave amplifiers, oscillators and other active components, used in various communication systems, requires accurate knowledge of the active device's (microwave transistor's) RF characteristics. It is in general insufficient and inaccurate for the transistors operating at high power with high signal compression in their strongly non-linear regions to be described using analytical or numerical models only [2]. Instead the devices must be characterized using specialized test setups under the actual operating conditions (FIG. 1).
A popular method for testing and characterizing such microwave transistors for high power operation is “load pull” and “source pull” [1]. Load pull or source pull are measurement techniques employing microwave tuners (2, 4) and other microwave test equipment (1, 5). The impedance tuners, in particular, are used in order to manipulate the microwave impedance conditions under which the Device Under Test (DUT, or transistor) (3) is tested (FIG. 1). Tuners (2, 4) and measurement instruments (1, 5) are digitally controller (6, 7 and 8) by a system control computer (9).